(a) Field of the Invention
The present invention relates generally to a camera, and more particularly to a sprocket mechanism for cameras which utilizes rotation of a sprocket to obtain an electrical detection signal for effectively determining the state of advancement and positioning of the frames of a film roll as well as displaying the number of advanced frames.
(b) Description of the Prior Art
The parent patent application of the present invention is directed to an improvement on the sprocket mechanism for facilitating advancement of film rolls of a new film system. In the parent application, the sprocket mechanism comprises a sprocket having a body provided with two pawls spaced apart from each other a predetermined distance at a periphery thereof, a first gear located at an upper side thereof and provided with a notch at a suitable position at its periphery, a transmission wheel forming a second gear at the upper side of the sprocket, the second gear having a shaft extending from a bottom side thereof for fitting and freely displacing in a central hole of the first gear, the shaft being fitted with a stop element having a vertical section at a rear end thereof, the vertical section being retained in the notch of the first gear, thereby allowing the sprocket, transmission wheel and the stop element to synchronously rotate when the pawls of the sprocket engage the positioning holes of the film; after the sprocket has rotated through a determined angle, the pawls will contact the film so that the stop element will absorb the rotational speed from the transmission wheel, achieving precise advancement of a single frame of film. The present invention is directed to enhancing the effectiveness of the sprocket mechanism disclosed in the parent application.